zoj 1589 Professor John

把不等式A 那么所有不等式就可以组合成一张有向无环图
然后只需对每个点bfs，从bfs的第二层开始记录即可

#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;
int vis[27];
map<int, vector<int>> ans;
map<int, vector<int>> mp;
set<int> from;
void bfs(int sorce) {
	memset(vis, 0, sizeof(vis));
	vis[sorce] = 1;
	queue<int> q;
	q.push(sorce);
	int cur, t, sz, i, j, len;
	t = 0;
	while (!q.empty()) {
		sz = q.size();
		t++;
		for (i = 0; i < sz; i++) {
			cur = q.front();
			q.pop();
			if (t > 2)ans[sorce].push_back(cur);
			vector<int> to = mp[cur];
			len = to.size();
			for (j = 0; j < len; j++) {
				if (!vis[to[j]]) {
					vis[to[j]] = 1;
					q.push(to[j]);
				}
			}
		}
	}
}

int main() {
	int T, m, i, coun, len;
	char ch[10];
	scanf("%d", &T);
	coun = 0;
	while (T--) {
		scanf("%d", &m);
		mp.clear();
		ans.clear();
		for (i = 1; i <= m; i++) {
			scanf("%s", ch);
			if (ch[1] == '<') {
				mp[ch[0] - 'A'].push_back(ch[2] - 'A');
				from.insert(ch[0] - 'A');
			} else {
				mp[ch[2] - 'A'].push_back(ch[0] - 'A');
				from.insert(ch[2] - 'A');
			}
		}
		map<int, vector<int>>::iterator it;
		for (it = mp.begin(); it != mp.end(); it++) {
			bfs(it->first);
		}
		printf("Case %d:\n", ++coun);
		if (!ans.size())printf("NONE\n");
		else {
			set<int>::iterator it;
			for (it = from.begin(); it != from.end(); it++) {
				vector<int> v = ans[*it];
				sort(v.begin(), v.end());
				len = v.size();
				for (i = 0; i < len; i++) {
					printf("%c<%c\n", 'A' + *it, 'A' + v[i]);
				}
			}
		}
	}
}
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